Loading of signaling conductors



June 10, 1930. v. E. LEGG v LOADING OF SIGNALING CONDUCTORS Filed NQv. 8, 1928 Patented June 140, 1.930

UNrrsn STATES VICTOR LEGG, OF EAST ORAING-E, NEW JERSEY, ASSIGNOR TO BELL TELEPHONV'E LABORATORIES, INCORPORATED, OF NEW' YORK, N. Y., A CORPORATION OF 1\TEW YORK LOADING OF SIGNALING CONDfUCTORS Application'ied November s, 192s. serial no. 317,931.

This invention relates to long loaded submarine cables.

An object of the invention is to reduce iinpedence irregularities in taper loaded cables or conductors.

In long submarine cables the overall attenuation is so great that relatively large currents must be applied at one end in orderk lthat signals of suitable strength may be 1o received at the distant end. If the conductor is loaded with' magnetic material the permeability and hysteresis losses of which vary with the magnetizing force, the large variations in the current and hence the inagnetizing force in the terminal sections may cause the inductance and resistance due to the loading material to vary between wide limits during each cycle. As a result of` these variations in the inductance and' resistance of the conductor it is diiicult to construct an articial line that will simu- ,Y

late such a cable with sufficient exactness for duplex telegraph operationi If 'the cable is designed for telephone or carrier Jfrequency operation thereis the additional objection that the varying impedance produces intermodulation between dierent telephone and carrier frequencies with resultant distortion. Tapering the loading has beenproposed and eects a partial cure Jfor Vthese conditions.

In accordance with this invention the terminal sections are loaded with a greater thickness of loading material than the central sections. The material used Jfor loading the terminal sections has a low hysteresis loss, a lower resistivity than thecentral Y sections, and a high constancy of permea- The centralV portions of the conductor are loaded in the n usual manner with a magnetic material having high permeability and relatively high resistivity. By way of example, the central suitable material for loading the center sections is a composition containin approximately Ni,.23% Fe, 25% Cgo.7% Mo and 0.47 Si having after a' proper heat treatment an initialpermeability of about 87 .5, a'resistivity of about 82 microhm-cms. anda variation of permeability which, although reasonably small is `much greater than that of the material used to load the terminal section as will be describedv'hereinafter.- This particular composition and la discussion of the method of selecting a heat treatment needed to give a desired value yof initial permeability and other similar compositions which may be advantageously used for loading the central sections are described and claime'din Elmens U. S. Patent application 220,387, liled September 19, 1927.

The increasedl thickness of. loadingmaterial on the fterminal sections may be attained by Vmerely applying a loading tape proportionallythicker.' A preferred manner, however,`is to apply more layers. Thus twice as much material may be applied in two layers. However, it is not necessary that all the layers be of equal thickness.V

Subdivision ofthe layers possesses advantages which will be discussed hereinafter.

In the drawing, the loading tape 14 is of the same dimensions as Athat used on the central sections, the composition of this tape, however, being different, as will be describpermeability and the lower permeability material having the lower resistivity.

2. A conductor in accordance with claim l in which the resistivities are proportional to the permeabilities of the two magnetic materials.

8. A magnetically loaded conductor in which magnetic material of decreased resistivity on one portion of the conductor is more subdivided than magnetic material of greater resistivity on another portion.

4:. A long, loaded cable having the terminal sections loaded with a greater thickness of loading material than the central l5 section, the loading material on the terminal section having lower but more constant permeability and lower resistivity than that on the central section.

5. A cable in accordance with claim 4 characterized in this that the loading material of the terminal sections consists of a greater number of layers than that on a central section.

6.' A long submarine signaling conductor Y having great over-all attenuation, comprising cable sections loaded 'with a magnetic composition the essential constituents of which are nickel, iron and cobalt, the different cable sectionsV having dierent constancies of permeability and different re-v sistivities, characterized in this that the sections of greater constancy of permeability and lower resistivity are closer to the terminals of said conductor `than the section of greater resistivity and lower constancy ofV permeability. y

7. A submarine cable continuously loaded diierently in dierent portions of its length in such manner that the product of the permeability squared of the loading material by the number of layers thereof by the cube of the thickness per layer divided by the resistivity of the material for one section is approximately equal to the corresponding product for another section.

In witness whereof, I hereunto subscribe my name this 31st day of October, 1928.

VICTOR E. LEGG. 

